On Tuesday, May 22, NASA’s NICER (Neutron Star Interior Composition Explorer), an X-ray telescope on the International Space Station, developed a “light leak,” in which unwanted sunlight enters the instrument. While analyzing incoming data since then, the team identified an impact to daytime observations. Nighttime observations seem to be unaffected. The team suspects that at least one of the thin thermal shields on NICER’s 56 X-ray Concentrators has been damaged, allowing sunlight to reach its sensitive detectors.